Today I performed a frequency sweep on my m80's along with my av123 MFW-15 subwoofer. I ploted the frequecy response. I was shocked by the very uneven frequency response that was produced across the frequency range of 20hz up to 200hz.

There were peaks as high as 90db at 130hz and the lowest point was 57db at 97hz. That is an amazing 33db variation between maximum and minimum values.

Here I was thinking that my speakers were producing a very high quality smooth response across the frequency spectrum.

I have come to the conclusion that there are several possibilities as to why I have such a poor frequency response.

Either:1. The audyssey calibration of my speakers is not doing the job properly. I have an Onkyo 875 amp, my front speakers are set to large, calibration resulted in my m80's being automatically set to full range.

or2. The characteristics of my room have devasted the natural frequecy response of my m80's. I have solid timber floors (not ideal) and the room is large (20 ft x 45ft.) Is there anything I can do to correct any room related problems such as using bass traps?

2. The characteristics of my room have devasted the natural frequecy response of my m80's. I have solid timber floors (not ideal) and the room is large (20 ft x 45ft.) Is there anything I can do to correct any room related problems such as using bass traps?

Most of the problem is going to be your room. Room modes play hell with the frequency response from 20-200Hz. The first thing you can do is play with speaker/subwoofer and seat positioning. Just a few inches to a foot one way or another especially closer or farther from a room surface (including floors) can make a huge difference. Bass traps AFAIK are best for taming the FR between 100-200Hz loosing effectiveness the lower the frequency. Having multiple low frequency sources like more than one subwoofer and/or running your mains with “double bass” can also help even things out. Finally, EQ can help some though the EQ available is Audyssey is limited and has a hard time compensating for room modes across multiple seats since it has to come up with a compromise EQ solution. EQ for one seat especially with something purposed built to EQ low frequencies can have a profound effect. I’ve been testing SVS AS-EQ1 that Charles “CV” loaned me with fantastic results for a single seat but only marginal results across three seats but it only works for the LFE channel.

If you look at the 20Hz to 100Hz range your variation is 77dB to 95dB or about 18dB which is the same swing (different frequencies) that I’m getting on the “before curve” measured by the SVS AS-EQ1 for just the subwoofer in my room. Also, unless I missed a reading it looks like the largest swing from 20Hz to 200Hz is about 25dB from 70dB to 95dB which IMO looks similar in magnitude to what I’m seeing in my room. So I would say that your room is already looking better than mine.

As for what’s acceptable to you only your ears can determine that and now that you are measuring the FR the numbers are also going to start playing tricks on your head. I suggest doing some serious listening along with the measurements while continuing to tweak the existing setup you have. If you have some headphones that are reasonably flat from 200Hz to down below 100Hz that might be a better way to gauge how the FR of your speaker should sound w/o the room in the equation since I’ve noticed using both Audyssey and the AS-EQ1 that a few (+/- say 3) dB improvement here and there is hard to make out under real listening conditions.

Eventually you may want to consider room treatments to take care of the 100Hz to 200Hz range if tweaking speaker/seating placement doesn’t help enough. For the below 100Hz range multiple subwoofers is probably your best bet, and you’ve got a pretty big room so a little extra dB there might also help. Only after tweaking placement and using room treatments and multiple subs would I consider going beyond the EQ already available in your receivers Audyssey. IMO even a dedicated subwoofer EQ system like the AS-EQ1 can’t tame the low frequencies across multiple seats very well. Should know more today on how it performs with multiple subs as Sean is coming over with two of his for some testing.

Like Ken said try measuring with Audyssey off. When tweaking placement turn Audyssey off since it’s applying correction for that last setup it measured. Also, it’s better to find the best placement for you speakers and subwoofer and then run Audyssey. While Audyssey can help some people a lot it works best if you give it as much help as possible.

Hopefully some of our experts on this subject will chime in soon as most of my knowledge on this is still theoretical and several people here have done much more practical application in this area than I have.